Seems my previous post has taken on a life of its own and thats okay, thanks for all the good information and discussion.  However, has anyone ever necked the 32-20 down to 30 cal?  I think this would provide very interesting combination of components to explore.  Thanks

Yup, except with BP.  But the 30-20 isn't really new....  I use a 1in 12 twist barrel, and bullets up to 185 grs, swiss 1 1/2Fg.  My short range BP match rifle.
Using 17.9 with the Pope bullet, 18.4 with the 151 RN

I helped Jerry DeVaudruil build a 30-20 on a No.1 Ruger, barrel, 1-10 twist, not sure of the maker, but Jerry knew K. Bresien pretty well and had rifled barrels on his equipment
keep in mind he was 86yo or so 
So.

Jerry wanted to make the rifle in 30BR, I talked him into  the 30-20, mainly because I have a reamer set up for .30 cal bullets, and has a throat on it intended for 160-180 gr bullets fixed ammo
Jerry insisted on BS a 200 grain bullet with 11.5 grains of No. 9, because that's what everyone was doing
I expressed concern because he wanted to use one case like he has since he taught the Indians how to clean flintlocks
this will not work, second firing, the case had to be knocked out with a cleaning rod, some split and left the neck in the chamber, PIA to remove, had to use cerrosafe to get it out
gun shot well at 200 yds. but Jerry's eyes went bad, Glaucoma, and i think the rifle went to auction

We never come up with a powder that wasn't  a problem with breech seating,  I have a 30-20 on a No.2 RB, lined with TJ liner 1-10 tw, I use Reloder 7, or WC680, RCBS 30-180-sp, with good results shooting a local Silhouette match, will knock 200 yd, rams down, also with a PB Lyman 311241, and 308206

I have also made a number of 30-20 rifles from H&R shotguns, using 1-15, 30BR barrels, Bench Rest Take-offs that stopped shooting jacketed, and had been set back , a couple times
using mostly 120 grain bullets, PB, these rifles shoot better than they should, 

any answer more specific, ask

I have a couple rifles that are stalled because of the current market woes in getting barrels.  A .30-20 would be easier to get a barrel than a .32-20 since I’d just need to grab a blank off the rack.

The question I have….

Do you need a different reamer to do a .30-20, or can I just put a smaller pilot on my .32-20 reamer and get a usable chamber?

Nominal groove diameter of the 32-20 is .311, so the difference is quite small. I suspect new 32-20s might even use .308 barrels.
And to answer the question - I used a standard min-spec 32-20 reamer for chambering the barrel, a Lothar Walther 1 in 12 twist.  Then again, no sizing required when using BP.
I shoot the Pope 308403 semi breechseated, and a 151gr RN of my own design.
With the previous barrel, I also shot jacketed spitzer bullets.

327 Brass ain't exactly easy to find these days.

Interesting. I've noticed my HP barrels always seem to have 'something' left on the lands no matter what I clean them with. They're only 4 thou high, but maybe that's enough to isolate the surface and generate heat checking that BP could take advantage of?

As for 327 brass. If you're only going to use smokeless. 32 HR would maybe be easier to source? And maybe for load density anyway?

I tried this a few years ago and it worked in some but not all all rifles.The rim is a bit smaller and thinner and passed under some extractors.